Rev: 01
P/N: 95343
Page | 11
Selecting Calibration Standards
For best results, choose a calibration standard whose value is close to what you expect to see in the water
you’re measuring. For example, calibrate with a 1413 μS/cm Specific Conductance standard if you expect to see
Specific Conductance readings between 500 and 1500 μS/cm in the field. Similarly, if your waters tend toward
being acidic (below 7) rather than basic (above 7), calibrate with a 4-buffer instead of a 10-buffer in addition to
the 7-buffer base calibration.
Sensor
Standard Method of Calibration
Available Calibration Solutions
Comments
Temperature
Never requires calibration
N/A
pH / pH Reference
2 or 3 points
pH 4, pH 7, pH 10
pH 7, pH 10 most common
ORP
1 Point
ORP Standard Solution, such as
ZoBell’s or Light’s solution
ORP standards can range from
200 – 475 mV, any will work
Conductivity
1 Point
CD Standard, 0.5 Molar, 58670 Micro S
CD Standard, 0.1 Molar, 12856 Micro S
CD Standard, 0.01 Molar, 1412 Micro S
CD Standard, 0.001 Molar,147 Micro S
brackish/saltwater borderline
brackish water typical
freshwater very pure
fresh/glacial water
Reference Electrode
calibration not required
N/A
replace pH electrolyte
solution at routine calibration
Depth
Adjust for barometric pressure
N/A
Recalibrate at deployment
site for best accuracy
Turbidity
2 points
0 NTU, 10 NTU, 100 NTU, 400 NTU
calibrate near expected value
HDO (Optical DO)
calibrate at 100% saturated water
DI water -shake vigorously to
oxygenate
set BP before calibrating,
recalibrate at deployment site
for best accuracy
Temperature
The Temperature sensor is an electrical resistor (thermistor)
whose resistance changes predictably with temperature. The
sensor is protected by a stainless-steel tube. Thermistors are very
stable with time, and so do not require calibration.
Dissolved Oxygen (DO)
The optical dissolved-oxygen sensor uses fluorescence combined
with a membrane cap made of an oxygen active compound to
measure oxygen. When the sensing surface is exposed to water or
air, oxygen diffuses into the sensing surface according to the
amount of oxygen in the water. The sensor output is corrected for
the temperature and salinity of the water.
